Those are some great plans of Cairo, but we should keep in mind that the City class gunboats, designed as warships, differed from tinclads which were conversions of commercial steamboats. Most notably the tinclads were side- or stern-wheelers while the Citys had the paddle wheel in the unusual but better-protected position inside the casemate. The Citys were also wider in proportion to their length than most tinclads.
That said, the forward part of the casemate, where much of the armament was located, might have been fairly similar.